In U.S. Pat. No. 2,758,124, methyldichlorosilane and trimethylchlorosilane are reacted with a large excess of water to produce trimethylsilyl-terminated methylhydrogenpolysiloxanes. However, the process is difficult to control and leads to branching in the polysiloxane chain or even gelling of the product. HCl generated appears as hydrochloric acid.
DE-A-1 125 180 describes a process in which, in a first step, methyldichlorosilane and trimethylchlorosilane are hydrolyzed with 1 mol of water per mole of hydrolyzable chlorine in concentrated hydrochloric acid. The concentrated hydrochloric acid contains tetrahydrofuran. In a second step, the crude hydrolysate is admixed with a large amount of water. The oil thus produced is resistant to gelling. However, in this process, large amounts of tetrahydrofuran-containing concentrated hydrochloric acid, as well as dilute hydrochloric acid occur, neither of which can be economically reworked.